1. Field of the Invention
The present invention relates to a technology for performing communication between a plurality of communication terminals and, more particularly, to a technology for allowing a wireless communication terminal to participate in a wireless network efficiently.
2. Description of the Related Art
With the realization of miniaturization and lightweight of information terminals, it has become common for people to carry an information terminal. Wireless communication environment in which a plurality of users can enjoy an application such as game together using infrastructure such as base stations and access points has become a reality in recent years. Study has also been vigorously undertaken on the construction of wireless ad hoc network for on-demand communication. In an ad hoc network, base stations and access points are not necessary. It is therefore easy to build a wireless network even in places where no such infrastructure exists. In an ad hoc network, a plurality of users can enjoy a game together as they join each other, bringing their own portable game devices and communicating wirelessly.
An infrastructure network and an ad hoc network are built using technologies such as IEEE802.11 or Bluetooth. A wireless communication environment assumed conventionally is such that several terminals are brought together so that communication is achieved between the terminals. In an infrastructure network or an ad hoc network, however, a situation could occur in which as many as 10-100 terminals are brought together in the same environment.
In a wireless network using IEEE802.11, a Basic Service Set (BSS) is prescribed as a basic unit of group comprising terminals communicating with each other. BSS refers to a set which is a group of mutually communicating terminals. Terminals belonging to the same BSS can communicate with each other. A BSS is identified by an 48-bit identifier known as Basic Service Set ID (BSSID). A unique value in the environment is assigned to a BSSID. There is also available a Service Set ID (SSID) comprised of a character string of 0-32 bytes to discriminate between BSSs. SSID is arbitrary set. The same SSID may be assigned to a plurality of BSSs. A BSS is formed by a terminal or an access point transmitting a reference packet called beacon. The range reached by the beacon defines a spatial range of the BSS. A plurality of BSSs may be located in the same physical space.
When using a wireless network using IEEE802.11, a terminal is required to belong to one of the BSSs available. For this purpose, the terminal searches for (scans) BSSs located in its neighborhood. When participating in an existing group, the terminal may specify an SSID in case it has the knowledge of the SSID of a group in which participation is sought. In contrast, if the SSID is not known, the terminal scans all BSSs in its neighborhood and specifies an SSID selected from the SSIDs identified as a result of the search. It will be noted that the search for all BSSs is equivalent to a search designating ANY as the SSID.
Thus, when a large number of BSSs exist in the neighborhood and when a terminal does not have the knowledge of the SSID of the BSS in which participation is sought, the terminal should designate ANY so as to list all BSSs in the neighborhood to allow the a user to select and designate a desired BSS in the list. Data related to a BSS has attached thereto a variety of information. By listing the information on all BSSs in the neighborhood, the list grows large disadvantageously when there are a large number of BSSs. To address this, a sufficient storage area for retaining the list should be reserved. It is unfavorable, however, to enlarge the capacity of a memory merely for the purpose of retaining the list. Another problem is that it takes a long period of time for the terminal to identify the BSS in which it seeks participation because all BSSs existing in the neighborhood are listed. In this background, it is required to efficiently prepare a list of BSSs that are candidates for connection.